Variable unbalanced weight mechanism for mechanical vibrating screens and the like



Sept. 6, 1949.

VAR

O R STRAWN IABLE UNBALANCED .WEI-GHT MECHANISM FOR MECHANICAL VIBRATING SCREENS AND THE LIKE Filed Jan. 5, 1949 [/vvE/vTo/Q; YOIQVAL. R-5TEAWN,

HTT'Y attached to the shaft it.

Patented Sept. :6, 1949 ARIABLE UNBALANCED WEIGHT MECH- ANISM FOR MECHANICAL VIBRATING SCREENS AND THE LIKE I Orval R. Strawn, Columbus, Ohio, assimor to The Jeffrey Manufacturing Company: corporation of Ohio Application January 8, 1939 SerialNo. 68,893

2 Claims.

This invention relates to an unbalanced weight mechanism for vibratory screens or other vibratlng apparatus, and an object of the invention is to provide an improved and emcient mechanism of the above mentioned type, in which the effective weight as well as the effective lever arm of the unbalanced weight is adjusted automatically in response to speed variations to reduce undesirable violent vibrations or jouncing during starting and stopping of the vibratory mechanism.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

In the accompanying drawings,

Fig. 1 is a sectional view through a screen incorporating the features of my invention, the sectional view of the unbalanced weight mechanism being taken on the line l--l of Fig. 2, looking in the direction of the arrows;

Fig. 2 is an end view of one of the unbalanced weight mechanisms, the enclosing cover for the housing thereof being removed, with the parts shown in the running position;

Fig. 3 is a view similar to Fig. 1, with the parts shown in the idle position; and

Fig. 4 is a sectional view taken on the line 4-2 of Fig 2, looking in the direction of the arrows.

In the embodiment of my invention, as illustrated particularly in Fig. 1 of the drawings, there is a screen deck ill which is preferably mounted on four flexible hangers, two of which are seen at M, ii. The deck ill is provided with a screen cloth l2. Extending transversely of the deck HI and on a horizontal axis is a rotating shaft l3 carried in appropriate hearings on said deck it. At each end of the shaft it there is an unbalanced weight mechanism M, the two mechanisms it being of substantially the same construction, except that the one on the right, as viewed in Fig. i, is provided with a drive pulley l5 by which the two interconnected unbalanced weight mechanisms it are driven.

Each of the mechanisms it includes a generally cylindrical caslng it having a removable cover plate ii, one of which plates carries the pulley it. The casing l6 includes an integral upright inner wall or base it which is rigidly Extending outwardly from the Walt it is a pair of pivot pins i9 and 2%, each of which is rigidly attached at its bottom to said wall or base It. The axes of the pivot pins it and 22 are parallel to each other and to the axis of the shaft it and in one position of adjustment of the parts, as illustrated for example in Figs. 2 and 3 of the drawings, the pins iii and 2t are equidistant from a plane passing through the axis of shaft It. At their outer ends the pivot pins l9 and 2t carry pivoted arms 2i and 22, respectively.

interconnecting each of the pivot pins 59 and with its associated arms 2| and 22 is a helical spring, which springs urge the two arms 2i and 22 in reverse directions, urging the arm 2! in a clockwise direction and the arm 22 in a counterclockwise direction, as viewed in Fig. 2 of the drawings, or, stated anotherway, urging the arms 2! and 22 to their idle positions as illustrated in Fig. 3 of the drawings. The spring interconnectlng pin i9 and arm 2! is designated 23, and the spring interconnecting pin 20 and arm 22 is designated 22.

At their free ends the arms 2i and 22 carry weights or masses and 26, respectively. Intermediate their ends th arms 21 and 22 carry oppositely extending pins 21 and 28, respectively, which overlap each other and, which is of more significance, they are received in a loop type linkage 29 which is connected to a weight or mass mounted for rectilinear reciprocatory motion on a pair of spaced pins 3i rigidly attached to the interior cylindrical surface of easing Hi. The loop type linkage or bracket 29 provides for swinging movement of the arms 2i and 22 about the pins I9 and 20, respectively, while interconnecting said arms and their associated weights 25 and 26 with the rectilinearly movable weight 30.

The above mentioned plane which equally separates the pivot pins l9 and 20 not only passes through the axis of shaft l3 but is parallel with the rectilinear axis of movement of the weight or mass 30. In fact, the center of gravity of said weight 30 is preferably always in this plane.

It is, of course, evident that when the unbalanced weight mechanisms l4 rotate, every part thereof which has weight is a factor in determining the overall'or total effective unbalanced weight. Furthermore, the distance between the center of gravity of each total unbalanced weight and the spin axis of the mechanism determines the amount of energy available to vibrate the deck l0.

Each of the similar unbalanced weight mechanisms i4 is so constructed that the effective weight or mass of the resultant unbalanced weight, as well as the distance of the center of gravity thereof from the spin axis, vary as the parts move from the idle position to the running position, and vice versa. This variation in both the effective mass and the effective lever arm through which it works is, employed to prevent jouncing or severe uncontrolled vibration of the unit during starting and stopping which is a known characteristic of fixed mass and fixed lever arm unbalanced weight mechanisms.

When the parts are in the idle position, as illustrated in Fig. 3, it is evident that the unbalanced weight provided by the arms 2! and 22 and the pins l9 and 20 is to the left of a vertical plane which passes through the geometrical axis of the 2d shaft it. On the other hand, the center of gravity of the weight 30 is to the right of this vertical plane. The centers of gravity of the weights 25 and 26, considered alone, are very near this plane and may be either to the right or to the left thereof. However, the resultant of all the weights of each unbalanced weight mechanism I 4, when i it is idle, is that it is slightly eccentric to the geometrical axis of the shaft i3 in the direction in which the rectilinearly movable weight 30 moves as it is moved by centrifugal force upon rotation of the shaft l3.

When the unit is first started the shaft l3 will rotate around its geometrical axis and there will be no significant vibration of the deck Iii. The above mentioned effective overall weight of the various parts of each mechanism I4 is suificient to create a force, in response to said rotation, which will urge the mass 30 rectilinearly outwardly from said geometrical axis. It is particularly significant, however, that during the starting of the unit and likewise during the stopping the distance of this mass from the axis of rotation, be it either the normal spin axis or the geometrical axis of the shaft Hi, the distance between which is not of great significance insofar as the particular structure here claimed is concerned, is relatively small and the masses provided by the arms 2| and 22 are on the reverse side of a plane through the axis of rotation, either spin axis or geometric axis of shaft i3, tending to reduce its effective weight or mass.

After the unit has come up to speed the parts will be in the position illustrated in Fig. 2, in

which case the distance of the weight 30 from the spin axis will be a maximum, and the effective distance between the combined weights 25 and 26 will be a maximum with respect to the spin axis. Since these weights 25 and 26 are on opposite sides of the geometric axis of shaft l3 as well as its spin axis, they will, of course, tend substantially to counterbalance each other when in their idle positions, while in their running positions and intermediate positions they will, of course, tend to increase the effective weight of the total unbalanced mass.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and applicant therefore wishes not to be restricted to the,precise construction herein disclosed.

Having thus described and shown an embodiment of the-inventio what it is desired to secure by Letters Patent of the United States is:

1. Vibratory unbalanced weight mechanism including an unbalanced weight assembly, means mounting said assembly for rotary movement, said unbalanced weight assembly including a first weight, means mounting said first weight for rectilinear movement of its center of gravity toward and from an axis of rotation of said mechanism, a pair of pivoted arms, means pivotally mounting said arms for opposite swinging movement on spaced axes which are parallel with said axis of rotation and substantially equally spaced from a plane passing through said axis of rotation and parallel with the axis of rectilinear movement of said first weight, weights on the free ends of said arms, spring means urging the free ends of said arms and their attached weights away from each other whereby their combined center 01 gravity moves rectilinearly parallel with the movement of the center of gravity of said first weight and in a direction to counteract the unbalancing weight of said first weight, and a linkage between said first weight and said pivoted arms which moves said first weight to move the center of gravity thereof toward said axis of rotation when the free ends of said arms swing away from each other and which moves the center of gravity of said first weight away from said-axis of rotation when the free ends of said arms swing toward each other, the free ends of said arms and their attached weights when swinging toward each other also moving their combined center of gravity away from said axis of rotation in a direction to cooperate with said first weight to increase the total efiective unbalanced weight, the total unbalanced weight of the entire assembly being slightly off the axis of rotation in the aforementioned plane in the direction of movement of said first weight when it moves from said normal axis of vibration when the mechanism is at rest, all whereby both the total efiective unbalanced weight and the efiective distance thereof from the axis of rotation increase as the speed of rotation of said mechanism increases and decreases as the speed of rotation decreases.

2. Vibratory unbalanced weight mechanism including an unbalanced weight assembly, means mounting said assembly for rotary movement, said unbalanced weight assembly including a first weight, means mounting said first weight for rectilinear movement of its center of gravity toward and from an axis of rotation of said mechanism, a pair of pivoted arms, means pivotally mounting said arms for opposite swinging movement on spaced axes which are parallel with said axis of rotation and 'susbtantially equally spaced from a plane passing through said axis of rotation and parallel with the axis of rectilinear movement of said first weight, spring means urging the free ends of said arms away from each other whereby their combined center of gravity moves rectilinearly parallel with the movement of the center of gravity of said first weight and in a direction to counteract the unbalancing weight of said first weight, and a linkage between said first weight and said pivoted arms which moves said first weight to move the center of gravity thereof toward said axis of rotation when the free ends of said arms swing away from each other and which moves the center of gravity of said first weight away from said axis of rotation when the free ends of said arms swing toward each other, the free ends of said arms when swinging toward each other also moving their combined center of gravity away from said axis of rotation in a direction to cooperate with said first weight to increase the total effective unbalanced weight, the total unbalanced weight of the entire assembly being slightly oil. the axis of rotation in the aforementioned plane in the direction of movement of said first weight when it moves from said normal axis of vibration when the mechanism is at rest, all whereby both the total effective unbalanced weight and the effective distance thereof from the axis of rotation increase as the speed of rotation of said mechanism increases and decrease as the speed of rota- No references cited. 

